Plesk 11.0.9 supports only two password types, plain and sym, according to the feature "Enhanced security mode" (
Home > Tools & Settings > Security Policy
). The "plain" password type is used for new domains when "Enhanced security mode" is disabled; "sym" is used when the feature is enabled.

Other password types are not supported by Plesk 11.0 and cause the error when updating hosting preferences. Unsupported password types may appear in PP domains after migrating from another hosting platform.